639309805 has 4 divisors (see below), whose sum is σ = 767171772. Its totient is φ = 511447840.

The previous prime is 639309799. The next prime is 639309833. The reversal of 639309805 is 508903936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 107868996 + 531440809 = 10386^2 + 23053^2 .

It is not a de Polignac number, because 639309805 - 2¹³ = 639301613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63930976 + ... + 63930985.

It is an arithmetic number, because the mean of its divisors is an integer number (191792943).

Almost surely, 2^639309805 is an apocalyptic number.

It is an amenable number.

639309805 is a deficient number, since it is larger than the sum of its proper divisors (127861967).

639309805 is a wasteful number, since it uses less digits than its factorization.

639309805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127861966.

The product of its (nonzero) digits is 174960, while the sum is 43.

The square root of 639309805 is about 25284.5764251648. The cubic root of 639309805 is about 861.4639770740.

The spelling of 639309805 in words is "six hundred thirty-nine million, three hundred nine thousand, eight hundred five".